US20230099125A1 - Tunable led filament - Google Patents
Tunable led filament Download PDFInfo
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- US20230099125A1 US20230099125A1 US17/908,489 US202117908489A US2023099125A1 US 20230099125 A1 US20230099125 A1 US 20230099125A1 US 202117908489 A US202117908489 A US 202117908489A US 2023099125 A1 US2023099125 A1 US 2023099125A1
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
- F21K9/20—Light sources comprising attachment means
- F21K9/23—Retrofit light sources for lighting devices with a single fitting for each light source, e.g. for substitution of incandescent lamps with bayonet or threaded fittings
- F21K9/232—Retrofit light sources for lighting devices with a single fitting for each light source, e.g. for substitution of incandescent lamps with bayonet or threaded fittings specially adapted for generating an essentially omnidirectional light distribution, e.g. with a glass bulb
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
- F21K9/60—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
- F21K9/68—Details of reflectors forming part of the light source
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V3/00—Globes; Bowls; Cover glasses
- F21V3/04—Globes; Bowls; Cover glasses characterised by materials, surface treatments or coatings
- F21V3/049—Patterns or structured surfaces for diffusing light, e.g. frosted surfaces
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
- H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
- H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
- H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
- H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2103/00—Elongate light sources, e.g. fluorescent tubes
- F21Y2103/10—Elongate light sources, e.g. fluorescent tubes comprising a linear array of point-like light-generating elements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2109/00—Light sources with light-generating elements disposed on transparent or translucent supports or substrates
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2113/00—Combination of light sources
- F21Y2113/10—Combination of light sources of different colours
- F21Y2113/13—Combination of light sources of different colours comprising an assembly of point-like light sources
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2115/00—Light-generating elements of semiconductor light sources
- F21Y2115/10—Light-emitting diodes [LED]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
- H01L2933/0008—Processes
- H01L2933/0033—Processes relating to semiconductor body packages
- H01L2933/005—Processes relating to semiconductor body packages relating to encapsulations
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
- H01L33/52—Encapsulations
- H01L33/54—Encapsulations having a particular shape
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
Definitions
- the present invention relates to a color tunable and/or color temperature tunable LED filament.
- the present invention also relates to a retrofit light bulb comprising at least one such LED filament.
- Incandescent lamps are rapidly being replaced by LED (light emitting diode) based lighting solutions. It is nevertheless appreciated and desired by users to have retrofit lamps which have the look of an incandescent bulb. For this purpose, one can simply make use of the infrastructure for producing incandescent lamps based on glass and replace the filament with LEDs emitting white light. The appearances of these lamps are highly appreciated as they look highly decorative.
- US20170130906A1 (FIG. 26), in which a tubular enclosure has exactly one unitary layer over an LED device.
- Light scattering particles are dispersed in the (wavelength conversion) layer throughout a binder material along with nanoparticles and phosphor particles.
- index-matching the binder material with the phosphor particles reduces scattering within the wavelength conversion layer, which adversely affects the uniformity of the color temperature distribution in the LED filament, whereby the light scattering particles serve to mitigate this negative effect.
- LED filament lamps are not color controllable.
- RGB or CW-WW LEDs on a translucent (e.g. transparent) substrate.
- CW-WW LEDs on a translucent (e.g. transparent) substrate.
- RGB or CW-WW LEDs on a translucent (e.g. transparent) substrate.
- a color tunable and/or color temperature tunable light emitting diode (LED) filament comprising: an elongated carrier, the elongated carrier comprising a first major surface and a second major surface arranged opposite to the first major surface, a plurality of LEDs arranged in at least one linear array on the first surface of the elongated carrier, wherein the plurality of LEDs includes LEDs of different colors and/or different color temperatures, a first elongated transparent or substantially transparent layer covering the plurality of LEDs on the first surface and also at least partly covering the first major surface, and a first elongated light scattering layer, arranged to at least partially cover the first transparent or substantially transparent layer.
- LED light emitting diode
- the present invention is based on the understanding that the first (substantially) transparent layer and the first elongated light scattering layer may serve the purpose of a mixing chamber on the LED filament level, in which mixing chamber light of different colors and/or different color temperatures may be mixed, to achieve emission of light that may be omni-directional and homogeneous. This in turn means that a color and/or color temperature tunable LED filament lamp with uniform appearance can be obtained.
- the exterior surface of the first elongated light scattering layer may be regarded as the first exiting surface of the LED filament.
- the first elongated transparent or substantially transparent layer may define an inner volume of the aforementioned mixing chamber.
- substantially transparent layer may here be construed as the layer having a reflectance of less than 8% or less than 5%.
- the second major surface of the elongated carrier is at least partially covered by a second elongated transparent or substantially transparent layer, the second elongated transparent layer having a thickness T 2 , wherein a second elongated light scattering layer is arranged to at least partially cover said second elongated transparent or substantially transparent layer.
- This may provide for symmetric emission.
- the exterior surface of the second elongated light scattering layer may form a second exit window of the LED filament.
- T 2 may be in the range of 0.5 to 5 mm, preferably in the range of 0.8 to 4 mm, and more preferably in the range of 1 to 3 mm.
- the second major surface of the elongated carrier is at least partially covered by a second elongated light scattering layer, whereby the aforementioned second elongated (substantially) transparent layer is omitted. This may lead to a more compact LED filament while still providing useful mixing.
- the first (and second) elongated transparent or substantially transparent layer and the first (and second) elongated light scattering layer can be made of a polymer, for example silicone, with high thermal and optical properties. Furthermore, the first (and second) elongated transparent or substantially transparent layer and the first (and second) elongated light scattering layer can be flexible. Furthermore, the first elongated (and second) light scattering layer may comprise scattering particles, such as to Al 2 O 3 , BaSO 4 , TiO 2 , or silicone particles. The scattering particles may be arranged in a matrix, preferably a polymer matrix such as, but not limited to, silicone.
- the layers can for example be applied by suspending/printing techniques or by dip coating or spraying techniques.
- the present LED filament could have a circular or elliptical cross-section (e.g. the embodiment with the second elongated transparent or substantially transparent layer and the second elongated light scattering layer), or a semi-circular or semielliptical (in particular divided along the major axis) cross-section (e.g. an embodiment without the second elongated transparent or substantially transparent layer).
- the circular cross section may be aesthetically more preferable.
- the elongated carrier may be translucent, preferably transparent. In this way, light emitted by the LEDs and reflected back by the first elongated light scattering layer could pass through the elongated carrier next to the LEDs and exit the LED filament on its backside (e.g. though the aforementioned second major surface of the elongated carrier or though the aforementioned second exit window).
- the (transparent) elongated carrier can for example be made of glass, sapphire, quartz, ceramic material, or alternatively, polymer such as poly imide (PI).
- the elongated carrier can be rigid (for example made by glass, sapphire, or quartz) or flexible (e.g. a foil).
- a maximum distance D between a light output surface of the plurality of LEDs and the first elongated light scattering layer may be in the range of 0.5 to 5 mm, preferably in the range from 0.8 to 4 mm, and more preferably in the range from 1 to 3 mm.
- D represents the (maximum) thickness of the first elongated (substantially) transparent layer from the LEDs' light output surfaces to where the first elongated light scattering layer begins. Larger values of D on the one hand may further improve light mixing, while on the other hand, drive the appearance of the filament away from typical filaments.
- D may bring the aesthetics of the LED filament closer to that of conventional filaments, while reducing its mixing efficiency. While D generally should be larger than zero, the obtained effect of the above-mentioned ranges is an optimum with respect to improved mixing and mimicking a filament (of an incandescent lamp).
- Color control as well as color and color temperature control of the present LED filament can be achieved with RGB LEDs. Color temperature control can also be achieved with cool(er) white LEDs and warm(er) white LEDs.
- the present LED filament could also include both RGB and white LEDs. It is notable that the more the variety e.g. different color and/or color temperature of LEDs used within a filament, the better the mixing may need to be. This may be accomplished by, for instance increasing the thickness of the transparent layer(s) (larger D, and T 2 ), and/or increasing the reflectivity of the scattering layer(s).
- the plurality of LEDs includes green LEDs, red LEDs, and blue LEDs, wherein the plurality of LEDs are arranged in three linear arrays which are parallel and individually addressable, and wherein one of the three parallel and linear arrays contains the green LEDs, another one of the three parallel and linear arrays contains the red LEDs, and a third of the three parallel and linear arrays contains the blue LEDs.
- green LEDs red LEDs
- blue LEDs blue LEDs
- the plurality of LEDs includes green LEDs, red LEDs, and blue LEDs arranged alternately in a single linear array, wherein the green LEDs provide a green channel, wherein red LEDs provide a red channel, wherein the blue LEDs provide a blue channel, and wherein the green, red and blue channels are individually addressable.
- This provides for improved color mixing, because all LEDs may be symmetrically and centrally arranged (widthwise) in the mixing chamber formed at least by the first (substantially) transparent layer and the first elongated light scattering layer.
- the different LEDs may here be electrically connected using for example jumpers or a double Cu layer for connecting the same color LEDs to one another.
- the number of green LEDs (per filament) is preferably at least five, more preferably at least eight, and most preferably at least ten.
- the number of red LEDs (per filament) is preferably at least five, more preferably at least eight, and most preferably at least ten.
- the number of blue LEDs (per filament) is preferably at least five, more preferably at least eight, and most preferably at least ten.
- the number of green LEDs, red LEDs, and blue LEDs may be equal.
- the LED filament may for example have ten green LEDs, ten red LEDs, and ten blue LEDs.
- the plurality of LEDs includes cool(er) white LEDs and warm(er) white LEDs arranged alternately in a single linear array, wherein the cool white LEDs provide a cool white channel, wherein the warm white LEDs provide a warm white channel, and wherein the cool white and warm white channels are individually addressable. Similar to the previously mentioned embodiment, this provides for improved color (temperature) mixing, because all LEDs may be symmetrically and centrally arranged in the mixing chamber.
- the color temperature of the cool white LEDs is preferably more than 2700K, more preferably more than 3000K, most preferably more than 3300K.
- the color temperature of the warm white LEDs is preferably less than 2500K, more preferably less than 2300K, most preferably less than 2200K.
- the first elongated light scattering layer may have a reflectance in the range of 30% to 90%, preferably in the range of 50% to 90%, and more preferably in the range of 60% to 90%. This may provide for good color mixing, preventing spottiness, while obtaining a good efficiency.
- the first elongated light scattering layer may have an angular gradient in reflectance such that the reflectance is highest in a portion of the first elongated light scattering layer being substantially parallel to said first major surface of the elongated carrier.
- the reflectance may be higher at a top/distal portion of the first elongated light scattering layer than at side portions of the first elongated light scattering layer, seen transversely to the longitudinal direction of the LED filament.
- the LED filament has an elliptical or semielliptical cross-section, the portion with highest reflectance could be at the (upper) vertex, whereas the side portions with low(er) reflectance could be at the so-called co-vertexes.
- light from the LEDs emitted substantially normal to the light output surface may have a higher intensity in comparison to light emitted in other angular directions, it may be useful to have the aforementioned angular gradient in reflectance, in order to achieve a more effective light mixing and better all-around homogeneous light distribution.
- the first elongated light scattering layer may have a higher reflectance than the second elongated light scattering layer. This may lead to improved color and/or color temperature mixing and symmetric emission. The reason is that first elongated light scattering layer receives direct light from the LEDs, while the second elongated light scattering layer receives indirect light of the LEDs (i.e. light that has be scattered/reflected by the first elongated light scattering layer).
- the difference in reflectivity of the first and second elongated light scattering layers may for example be achieved by increasing the concentration of scattering particles in the first elongated light scattering layer compared to the second elongated light scattering layer and/or by increasing the thickness of the first elongated light scattering layer compared to the second elongated light scattering layer and/or by using scattering particles with higher reflectivity in the first elongated light scattering layer compared to the second elongated light scattering layer.
- the difference in reflectance of the first and second scattering layers may preferably be at least 20%, more preferably at least 30%, most preferably at least 40%.
- the second elongated light scattering layer may for example have a reflectance in the range of 8% to 35%, preferably in the range of 10% to 32%, and more preferably in the range of 12 to 30%.
- the first elongated light scattering layer and the second elongated light scattering layer may form a single all-around light scattering layer.
- the rest of the LED filament, including longitudinal side surfaces of the elongated carrier, may be completely surrounded by this single (tubular) all-around scattering layer.
- the aforementioned maximum distance D may be greater than the thickness T 2 of the second elongated transparent or substantially transparent layer, Preferably, 2*T 2 >D>1.2*T 2 .
- the obtained effect is improved color mixing and symmetric emission.
- the (transparent) elongated substrate may optically be part of the second transparent or substantially transparent layer.
- a maximum normal distance P 1 from the first major surface of the elongated carrier to the exterior surface of the first elongated light scattering layer may at least 1.5 times the maximum normal distance P 2 from the second major surface of the elongated carrier to the exterior surface of the second elongated light scattering layer. This may compensate for the fact that the (transparent) elongated substrate may optically be part of the second transparent or substantially transparent layer, in case they have the same or similar refractive indices.
- a retrofit light bulb comprising at least one LED filament according to the first aspect a transmissive envelope at least partly surrounding the LED filament(s), a controller electrically connected to the at least one LED filament, and a connector for electrically and mechanically connecting said light bulb to a socket.
- FIG. 1 demonstrates a side view of a retrofit light bulb including a plurality of LED filaments accommodated within an envelope.
- FIGS. 2 a and 2 b demonstrate cross sectional views of an LED filament comprising first transparent and scattering layers.
- FIGS. 3 a and 3 b demonstrate cross sectional views of an LED filament comprising first transparent and scattering layers, and second transparent and scattering layers.
- FIGS. 4 a and 4 b demonstrate different embodiments of the scattering layer of the LED filament.
- FIG. 5 demonstrates an embodiment of the LED filament with a single all-around scattering layer.
- FIGS. 6 a - 6 c demonstrate the light distribution of LED filaments with and without the present inventive concept.
- FIGS. 7 a - 7 d demonstrate different embodiments of the carrier of the LED filament on which different types of LEDs are arranged in various configurations.
- FIG. 1 demonstrates a retrofit light bulb 100 including a plurality of LED filaments 20 , 22 , 24 accommodated within an envelope 10 .
- the LED filaments 20 , 22 , 24 (explained in more detail below) are connected to a controller 50 , and an electrical (and mechanical) connector 40 , through their connecting ends 12 and the connecting wires 30 .
- the light bulb 100 comprises an electrical connector 40 , here a threaded Edison connector such E26 or E27, in order to connect the lamp 10 to an electric socket (not shown).
- an electrical connector 40 here a threaded Edison connector such E26 or E27
- the LED filament 20 , 22 , 24 may be configured to emit white light, or light with any other color or spectrum.
- the LED filament 20 , 22 , 24 may also be configured to be color tunable and/or color temperature tunable (in case of white light). More details on the latter will follow later in the text.
- the tunability will then be controlled through the controller 50 shown in FIG. 1 .
- the controller 50 may be configured to control LEDs 210 of the LED filament individually.
- the LED filaments 20 , 22 , 24 of the lighting device 100 shown in FIG. 1 can be described as follows.
- FIG. 2 for example, demonstrates cross sectional views of such an LED filament 20 , with vertical line cuts along the width ( FIG. 2 a ), and the length ( FIG. 2 b ) of the LED filament 20 .
- the LEDs 210 are arranged on an elongated carrier 220 , for instance a substrate.
- carrier and “substrate” may be used interchangeably, and unless stated otherwise, are meant to imply the same meaning.
- the LED filament 20 , 22 , 24 has a length L and a width W, wherein L>5W.
- the width W of the LED filament 20 , 22 , 24 is preferably in the range of 3 to 10 mm, more preferably in the range of 4 to 8 mm, most preferably in the range of 5 to 7 mm.
- the obtained effect is improved mimicking a filament.
- the length L of the LED filament 20 , 22 , 24 is preferably longer than 30 mm, more preferably longer than 50 mm, most preferably longer than 100 mm.
- the obtained effect is improved mimicking a filament.
- the LED filament 20 , 22 , 24 is elongated having preferably an aspect ratio of the length L divided by the width W or height H of at least 10, more preferably at least 20, most preferably at least 30 such as for example 40 or 50.
- the LED filament 20 , 22 , 24 also has a height H.
- the height H of the LED filament is preferably in the range of 3 to 10 mm, more preferably in the range of 4 to 8 mm, most preferably in the range of 5 to 7 mm.
- the obtained effect is improved mimicking a filament.
- the LED filament 20 , 22 , 24 may be arranged in a straight configuration similar to FIG. 2 b , or in a non-straight configuration such as for example a curved configuration, a 2D/3D spiral or a helix.
- the LEDs 210 may be arranged in at least one linear array.
- the linear array in which the LEDs 210 are arranged may be in the direction of the elongated carrier 220 .
- the carrier 220 may be rigid (made from e.g. a polymer, glass, quartz, metal or sapphire) or flexible (e.g. made of a polymer e.g. a film or foil).
- a carrier 220 of rigid material may provide better cooling of the LED filament 20 , meaning the heat generated by the LEDs 210 may be distributed by the rigid substrate 220 .
- a carrier 220 of flexible material may provide shape freedom for designing the aesthetics of the LED filament 20 , 22 , 24 due to flexibility. It should be noted that, the thermal management of thin, flexible material may typically be poorer compared to rigid material. However, on the other hand, having rigid material as the substrate 220 , may limit the shape design of the LED filament 20 , 22 , 24 .
- the carrier 220 may have a first major surface 222 , and a second major surface 224 .
- the LEDs 210 are arranged on at least one of these surfaces. In the embodiment demonstrated in FIG. 2 b , and all of the following figures, the LEDs 210 are arranged on the first major surface 222 of the elongated carrier 220 .
- the carrier 220 may be reflective or light transmissive, such as translucent and preferably transparent.
- the carrier 220 may have a thickness of T subs .
- the LED filament 20 may comprise a first elongated transparent layer 230 , situated such to (at least partially) cover the LEDs 210 , and at least partially cover the first major surface 222 of the carrier 220 .
- a first elongated light scattering layer 240 is positioned so to cover the first transparent layer 230 , such that the first transparent layer 230 is sandwiched between the carrier 220 and the first scattering layer 240 .
- the normal maximum distance D between a light output surface 215 of the LED 210 and the first scattering layer 240 represents the optical path forward-emitted light from the LED 210 will traverse in the first transparent layer 230 .
- the combined effect of the first transparent layer 230 and the first scattering layer 240 is that they effectively provide for a mixing chamber, in which emitted light from the LEDs 210 in operation may be mixed.
- the scattering of light within the first scattering layer 240 may randomize the location from which light is emitted along the length L of the LED filament 20 , hence providing a more homogeneous appearance of light exiting a first exiting surface 245 of the LED filament 20 .
- Some light may be backscattered from the first scattering layer 240 towards the elongated carrier 220 . In the case of the elongated carrier 220 being transparent, the back scattered light may traverse the volume of the carrier 220 and exit the filament from the second major surface 224 .
- FIG. 3 demonstrates cross sectional views of another embodiment of the LED filament 22 according to this invention, with vertical line cuts along the width, and the length ( FIGS. 3 a and 3 b respectively).
- the LED filament 22 comprises a second elongated transparent layer 260 positioned to (at least partially) cover the second major surface 224 of the elongated carrier 220 , and a second elongated light scattering layer 250 positioned so to (at least partially) cover said second elongated transparent layer 260 .
- the second elongated transparent layer 260 has a thickness of T 2 .
- the combined effect of the second transparent 260 and scattering 250 layers is to effectively provide for a mixing chamber in which back scattered light from the first scattering layer 240 , and side-emitted light from the LEDs 210 can be mixed, so to provide for a more homogeneous appearance for light exiting a second exit surface 255 of the LED filament 22 .
- the carrier 220 should be light transparent, otherwise providing a mixing chamber on the second major surface 224 of the carrier 220 will be redundant.
- the second transparent layer 260 has a thickness of T 2 .
- D is larger than T 2 . This is to provide for a more optimal all-around light distribution from the LED filament 22 .
- the maximum normal distance P 1 from the first major surface 222 of the elongated carrier 220 to the exterior surface of the first elongated light scattering layer 240 may be at least 1.5 times the maximum normal distance P 2 from the second major surface 224 of the elongated carrier 220 to the exterior surface of the second elongated light scattering layer 250 .
- the transparent layers 230 , 260 , and the scattering layers 240 , 250 can be applied by suspending/printing techniques.
- the layers 230 , 240 , 250 , 260 can be applied by dip coating or spraying techniques onto the carrier 220 on which the LEDs 210 are arranged on.
- the transparent layers 230 , 260 , and the scattering layers 240 , 250 are preferably flexible, and are preferably Silicone materials.
- the scattering properties of the scattering layers 240 , 250 may be achieved by through the inclusion of light scattering particles 242 , 252 in these layers.
- the scattering of the first scattering layer 240 is preferably higher than that of the second scattering layer 250 . That is for further improving the light mixing of forward-emitted light exiting the first exiting surface 245 and the back scattered and/or side-emitted light from the second exiting surface 255 , so that they have a similar distribution, leading to an improved symmetry.
- FIG. 4 depicts exemplifying embodiments of an LED filament 22 in which the first scattering layer 240 is relatively more scattering than the second scattering layer 250 .
- the thickness S 1 of the first scattering layer 240 is generally larger than the thickness S 2 of the second scattering layer 250 .
- the optical path through which forward-emitted light is required to traverse through the first scattering layer 240 is increased, so that consequently the average number of scattering events will be increased in comparison to light traversing the second scattering layer 250 .
- the density and/or material of the scattering particles 242 , and 252 of the first 240 and second 250 scattering layers are different.
- the density and/or material comprising the scattering particles 242 of the first scattering layer 240 is higher compared to the scattering particles 252 of the second scattering layer 250 . This may insure an increase in the average number of scattering events light may encounter in the first scattering layer 240 compared to that of the second scattering layer 250 .
- S 1 and S 2 may be uniform.
- a first side surface 226 and a second side surface 228 of the elongated carrier 220 of the embodiments depicted in FIGS. 1 - 4 are bare. It is noted that some of the light traversing through the thickness T subs of the carrier 220 may escape through these first 226 and second 228 side surfaces. As mentioned, light may be mixed within the volume of the transparent elongated carrier 220 , and additionally in the second transparent layer 260 in embodiments comprising a second transparent layer 260 (embodiments of FIGS. 2 - 4 ), where the transparent elongated carrier 220 may be optically considered as a portion of the second transparent layer 260 . Additionally, for ensuring a better all-around light distribution from the filament 20 it may be useful that the first 226 and second 228 side surfaces of the carrier 220 are also covered by a scattering layer.
- the first 226 and second 228 side surfaces of the carrier 220 are covered by a scattering layer 280 .
- the first scattering surface 240 and the second scattering surface 250 are merged so to form a single, all-around scattering layer 280 , which circumferentially encompasses the rest of the LED filament 24 .
- the scattering property of the all-around scattering layer 280 may differ from portion to portion in an angular gradient manner. This again, is to further improve the even all-around light distribution from the filament 24 .
- the portion 228 of the all-around scattering layer 280 which is substantially parallel to the elongated carrier 220 /light output surface 215 of the LED 210 , has the highest scattering effect so to compensate for the higher intensity of the direct-emitted light from the LEDs 210 , emitted in a direction substantially normal to that of the output surface 215 of the LEDs 210 .
- the angular scattering gradient of the single all-around scattering layer 280 is accomplished by a gradual change in the thickness of this scattering layer 280 .
- the thickness, hence scattering properties of the all the single all-around scattering layer 280 has a mirrored symmetry around an axis X normal to the length of the elongated carrier 220 .
- the reflectivity, hence scattering, may be equal, and the lowest in portions R 1 -R 4 of the single all-around scattering layer 280 .
- These portions have a reflectivity of preferably less than 30%, more preferably less than 25%, most preferably less than 20%.
- portions R 5 -R 8 have are higher than that of R 1 -R 4 , and have an increasing gradient in their reflectivity as follows: R 5 ⁇ R 6 ⁇ R 7 ⁇ R 8 . These portions together with their mirrored portions position-wise largely correspond with that of the first scattering layer 240 of the previous embodiments, therefore are required to have a relatively higher scattering effect compared to R 1 -R 4 .
- Portion R 8 has the highest reflectivity being preferably more than 50%, more preferably more than 60%, most preferably more than 70%.
- the all-around scattering layer 280 can be referred to as a diffuser.
- the scattering layer (diffuser) 280 can be made e.g. by dispensing, or a (shrink) tube.
- FIGS. 6 a through 6 c shows a schematic comparison of the light distribution resulting from different LED filaments.
- the filaments 16 , 17 , and 24 are perpendicular to the plane of the page, at the center of the graph 600 .
- FIG. 6 a depicts the light distribution E of a conventional LED filament 16 in which the carrier is reflective, thus light cannot traverse the carrier.
- the envelope light distribution E light emitted from this LED is non-homogeneous, being less bright on the sides as opposed to the top, and is solely emitted from the first exiting surface.
- FIG. 6 c demonstrates light distribution E′′ from a filament 24 according to the invention with the all-around light scattering layer (diffuser) 280 .
- the light distribution E′′ of the filament with the diffuser is substantially homogeneous, with an all-around symmetrical light distribution.
- FIG. 7 demonstrates embodiments of the LED filament 20 , 22 , 24 on which the LEDs 212 , 214 , 216 , 218 , 219 are arranged in different configurations.
- the R 212 , G 214 , and B 216 LEDs are arranged in three linear arrays: the R channel 12 , the G channel 14 , and the B channel 16 which are parallel and individually addressable, each contain the R 212 , G 214 , and B 216 LEDs respectively. (Each of the R 12 , G 14 , and B 16 channels may be addressed individually, and/or simultaneously.)
- FIG. 7 b illustrates a portion of the carrier 220 in which the R 212 , the G 214 , and the B 216 LEDs are arranged alternately in a single linear array on the first major surface 222 , wherein the G LEDs 214 provide a green channel 14 , wherein R LEDs 212 provide a red channel 12 , wherein the B LEDs 216 provide a blue channel 16 .
- the in order to have separate color channels, the R 212 , G 214 , and B 216 LEDs may be connected using jumpers or a double Cu layer 330 for connecting the same color LEDs to on another.
- this embodiment may further improve color mixing.
- each of the R, G, and B channels 12 , 14 , 16 may be addressed individually, and/or simultaneously.
- FIG. 7 c depicts a portion of the carrier 220 in which cool-white (color) 218 , and warm-white (color) 219 LEDs arranged alternately in a single linear array.
- the warm white LEDs 219 provide a warm white channel 19
- the cool-white LEDs 218 provide a cool-white channel 18 , such that these channels 18 , 19 are individually addressable, so to provide for color temperature tunability.
- FIG. 7 d illustrates an embodiment in which the plurality of LEDs include red LEDs 212 , green LEDs 214 , blue LEDs 216 , and white (e.g. cool or warm) LEDs 217 arranged alternately in a single linear array.
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Abstract
Description
- The present invention relates to a color tunable and/or color temperature tunable LED filament. The present invention also relates to a retrofit light bulb comprising at least one such LED filament.
- Incandescent lamps are rapidly being replaced by LED (light emitting diode) based lighting solutions. It is nevertheless appreciated and desired by users to have retrofit lamps which have the look of an incandescent bulb. For this purpose, one can simply make use of the infrastructure for producing incandescent lamps based on glass and replace the filament with LEDs emitting white light. The appearances of these lamps are highly appreciated as they look highly decorative.
- An example of an LED filament is disclosed in US20170130906A1 (FIG. 26), in which a tubular enclosure has exactly one unitary layer over an LED device. Light scattering particles are dispersed in the (wavelength conversion) layer throughout a binder material along with nanoparticles and phosphor particles. According to US20170130906A1, index-matching the binder material with the phosphor particles reduces scattering within the wavelength conversion layer, which adversely affects the uniformity of the color temperature distribution in the LED filament, whereby the light scattering particles serve to mitigate this negative effect.
- Current LED filament lamps are not color controllable. For producing LED filament lamps with a color and/or color temperature control one can make use of RGB or CW-WW LEDs on a translucent (e.g. transparent) substrate. However, for a nice appearance it is desired to have good color mixing and/or improved light distribution.
- It is an object of the present invention to overcome the above-mentioned problem.
- According to a first aspect of the invention, this and other objects are achieved by a color tunable and/or color temperature tunable light emitting diode (LED) filament, the LED filament comprising: an elongated carrier, the elongated carrier comprising a first major surface and a second major surface arranged opposite to the first major surface, a plurality of LEDs arranged in at least one linear array on the first surface of the elongated carrier, wherein the plurality of LEDs includes LEDs of different colors and/or different color temperatures, a first elongated transparent or substantially transparent layer covering the plurality of LEDs on the first surface and also at least partly covering the first major surface, and a first elongated light scattering layer, arranged to at least partially cover the first transparent or substantially transparent layer.
- The present invention is based on the understanding that the first (substantially) transparent layer and the first elongated light scattering layer may serve the purpose of a mixing chamber on the LED filament level, in which mixing chamber light of different colors and/or different color temperatures may be mixed, to achieve emission of light that may be omni-directional and homogeneous. This in turn means that a color and/or color temperature tunable LED filament lamp with uniform appearance can be obtained.
- The exterior surface of the first elongated light scattering layer may be regarded as the first exiting surface of the LED filament. Furthermore, the first elongated transparent or substantially transparent layer may define an inner volume of the aforementioned mixing chamber. The term ‘substantially transparent layer’ may here be construed as the layer having a reflectance of less than 8% or less than 5%.
- According to an embodiment of the LED filament, the second major surface of the elongated carrier is at least partially covered by a second elongated transparent or substantially transparent layer, the second elongated transparent layer having a thickness T2, wherein a second elongated light scattering layer is arranged to at least partially cover said second elongated transparent or substantially transparent layer. This may provide for symmetric emission. The exterior surface of the second elongated light scattering layer may form a second exit window of the LED filament.
- T2 may be in the range of 0.5 to 5 mm, preferably in the range of 0.8 to 4 mm, and more preferably in the range of 1 to 3 mm.
- According to another embodiment of the LED filament, the second major surface of the elongated carrier is at least partially covered by a second elongated light scattering layer, whereby the aforementioned second elongated (substantially) transparent layer is omitted. This may lead to a more compact LED filament while still providing useful mixing.
- The first (and second) elongated transparent or substantially transparent layer and the first (and second) elongated light scattering layer can be made of a polymer, for example silicone, with high thermal and optical properties. Furthermore, the first (and second) elongated transparent or substantially transparent layer and the first (and second) elongated light scattering layer can be flexible. Furthermore, the first elongated (and second) light scattering layer may comprise scattering particles, such as to Al2O3, BaSO4, TiO2, or silicone particles. The scattering particles may be arranged in a matrix, preferably a polymer matrix such as, but not limited to, silicone. The layers can for example be applied by suspending/printing techniques or by dip coating or spraying techniques.
- Furthermore, the present LED filament could have a circular or elliptical cross-section (e.g. the embodiment with the second elongated transparent or substantially transparent layer and the second elongated light scattering layer), or a semi-circular or semielliptical (in particular divided along the major axis) cross-section (e.g. an embodiment without the second elongated transparent or substantially transparent layer). The circular cross section may be aesthetically more preferable.
- The elongated carrier may be translucent, preferably transparent. In this way, light emitted by the LEDs and reflected back by the first elongated light scattering layer could pass through the elongated carrier next to the LEDs and exit the LED filament on its backside (e.g. though the aforementioned second major surface of the elongated carrier or though the aforementioned second exit window). The (transparent) elongated carrier can for example be made of glass, sapphire, quartz, ceramic material, or alternatively, polymer such as poly imide (PI).
- Furthermore, the elongated carrier can be rigid (for example made by glass, sapphire, or quartz) or flexible (e.g. a foil).
- A maximum distance D between a light output surface of the plurality of LEDs and the first elongated light scattering layer (in the normal direction of said first major surface of said elongated carrier) may be in the range of 0.5 to 5 mm, preferably in the range from 0.8 to 4 mm, and more preferably in the range from 1 to 3 mm. In other words, D represents the (maximum) thickness of the first elongated (substantially) transparent layer from the LEDs' light output surfaces to where the first elongated light scattering layer begins. Larger values of D on the one hand may further improve light mixing, while on the other hand, drive the appearance of the filament away from typical filaments. Similarly, smaller values of D may bring the aesthetics of the LED filament closer to that of conventional filaments, while reducing its mixing efficiency. While D generally should be larger than zero, the obtained effect of the above-mentioned ranges is an optimum with respect to improved mixing and mimicking a filament (of an incandescent lamp).
- Color control as well as color and color temperature control of the present LED filament can be achieved with RGB LEDs. Color temperature control can also be achieved with cool(er) white LEDs and warm(er) white LEDs. The present LED filament could also include both RGB and white LEDs. It is notable that the more the variety e.g. different color and/or color temperature of LEDs used within a filament, the better the mixing may need to be. This may be accomplished by, for instance increasing the thickness of the transparent layer(s) (larger D, and T2), and/or increasing the reflectivity of the scattering layer(s).
- According to an embodiment of the LED filament, the plurality of LEDs includes green LEDs, red LEDs, and blue LEDs, wherein the plurality of LEDs are arranged in three linear arrays which are parallel and individually addressable, and wherein one of the three parallel and linear arrays contains the green LEDs, another one of the three parallel and linear arrays contains the red LEDs, and a third of the three parallel and linear arrays contains the blue LEDs. This provides for a low-cost design.
- According to another embodiment of the LED filament, the plurality of LEDs includes green LEDs, red LEDs, and blue LEDs arranged alternately in a single linear array, wherein the green LEDs provide a green channel, wherein red LEDs provide a red channel, wherein the blue LEDs provide a blue channel, and wherein the green, red and blue channels are individually addressable. This provides for improved color mixing, because all LEDs may be symmetrically and centrally arranged (widthwise) in the mixing chamber formed at least by the first (substantially) transparent layer and the first elongated light scattering layer. The different LEDs may here be electrically connected using for example jumpers or a double Cu layer for connecting the same color LEDs to one another.
- The number of green LEDs (per filament) is preferably at least five, more preferably at least eight, and most preferably at least ten. The number of red LEDs (per filament) is preferably at least five, more preferably at least eight, and most preferably at least ten. The number of blue LEDs (per filament) is preferably at least five, more preferably at least eight, and most preferably at least ten. Furthermore, on the filament, the number of green LEDs, red LEDs, and blue LEDs may be equal. The LED filament may for example have ten green LEDs, ten red LEDs, and ten blue LEDs.
- According to yet another embodiment of the LED filament, the plurality of LEDs includes cool(er) white LEDs and warm(er) white LEDs arranged alternately in a single linear array, wherein the cool white LEDs provide a cool white channel, wherein the warm white LEDs provide a warm white channel, and wherein the cool white and warm white channels are individually addressable. Similar to the previously mentioned embodiment, this provides for improved color (temperature) mixing, because all LEDs may be symmetrically and centrally arranged in the mixing chamber. The color temperature of the cool white LEDs is preferably more than 2700K, more preferably more than 3000K, most preferably more than 3300K. The color temperature of the warm white LEDs is preferably less than 2500K, more preferably less than 2300K, most preferably less than 2200K.
- The first elongated light scattering layer may have a reflectance in the range of 30% to 90%, preferably in the range of 50% to 90%, and more preferably in the range of 60% to 90%. This may provide for good color mixing, preventing spottiness, while obtaining a good efficiency.
- The first elongated light scattering layer may have an angular gradient in reflectance such that the reflectance is highest in a portion of the first elongated light scattering layer being substantially parallel to said first major surface of the elongated carrier. In other words, the reflectance may be higher at a top/distal portion of the first elongated light scattering layer than at side portions of the first elongated light scattering layer, seen transversely to the longitudinal direction of the LED filament. In case the LED filament has an elliptical or semielliptical cross-section, the portion with highest reflectance could be at the (upper) vertex, whereas the side portions with low(er) reflectance could be at the so-called co-vertexes. Since light from the LEDs emitted substantially normal to the light output surface may have a higher intensity in comparison to light emitted in other angular directions, it may be useful to have the aforementioned angular gradient in reflectance, in order to achieve a more effective light mixing and better all-around homogeneous light distribution.
- The first elongated light scattering layer may have a higher reflectance than the second elongated light scattering layer. This may lead to improved color and/or color temperature mixing and symmetric emission. The reason is that first elongated light scattering layer receives direct light from the LEDs, while the second elongated light scattering layer receives indirect light of the LEDs (i.e. light that has be scattered/reflected by the first elongated light scattering layer). The difference in reflectivity of the first and second elongated light scattering layers may for example be achieved by increasing the concentration of scattering particles in the first elongated light scattering layer compared to the second elongated light scattering layer and/or by increasing the thickness of the first elongated light scattering layer compared to the second elongated light scattering layer and/or by using scattering particles with higher reflectivity in the first elongated light scattering layer compared to the second elongated light scattering layer. The difference in reflectance of the first and second scattering layers may preferably be at least 20%, more preferably at least 30%, most preferably at least 40%. The second elongated light scattering layer may for example have a reflectance in the range of 8% to 35%, preferably in the range of 10% to 32%, and more preferably in the range of 12 to 30%.
- The first elongated light scattering layer and the second elongated light scattering layer may form a single all-around light scattering layer. Here the rest of the LED filament, including longitudinal side surfaces of the elongated carrier, may be completely surrounded by this single (tubular) all-around scattering layer.
- The aforementioned maximum distance D may be greater than the thickness T2 of the second elongated transparent or substantially transparent layer, Preferably, 2*T2>D>1.2*T2. The obtained effect is improved color mixing and symmetric emission. The reason is that the (transparent) elongated substrate may optically be part of the second transparent or substantially transparent layer.
- Furthermore, a maximum normal distance P1 from the first major surface of the elongated carrier to the exterior surface of the first elongated light scattering layer may at least 1.5 times the maximum normal distance P2 from the second major surface of the elongated carrier to the exterior surface of the second elongated light scattering layer. This may compensate for the fact that the (transparent) elongated substrate may optically be part of the second transparent or substantially transparent layer, in case they have the same or similar refractive indices.
- According to a second aspect of the invention, there is provided a retrofit light bulb, comprising at least one LED filament according to the first aspect a transmissive envelope at least partly surrounding the LED filament(s), a controller electrically connected to the at least one LED filament, and a connector for electrically and mechanically connecting said light bulb to a socket.
- It is noted that the invention relates to all possible combinations of features recited in the claims.
- These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.
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FIG. 1 demonstrates a side view of a retrofit light bulb including a plurality of LED filaments accommodated within an envelope. -
FIGS. 2 a and 2 b demonstrate cross sectional views of an LED filament comprising first transparent and scattering layers. -
FIGS. 3 a and 3 b demonstrate cross sectional views of an LED filament comprising first transparent and scattering layers, and second transparent and scattering layers. -
FIGS. 4 a and 4 b demonstrate different embodiments of the scattering layer of the LED filament. -
FIG. 5 demonstrates an embodiment of the LED filament with a single all-around scattering layer. -
FIGS. 6 a-6 c demonstrate the light distribution of LED filaments with and without the present inventive concept. -
FIGS. 7 a-7 d demonstrate different embodiments of the carrier of the LED filament on which different types of LEDs are arranged in various configurations. - As illustrated in the figures, the sizes of layers and regions may be exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.
- The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.
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FIG. 1 demonstrates a retrofitlight bulb 100 including a plurality ofLED filaments envelope 10. TheLED filaments controller 50, and an electrical (and mechanical)connector 40, through their connecting ends 12 and the connectingwires 30. Similar to the typical incandescent light bulbs, here inFIG. 1 , thelight bulb 100 comprises anelectrical connector 40, here a threaded Edison connector such E26 or E27, in order to connect thelamp 10 to an electric socket (not shown). Note that in this text, retrofit light bulb and lamp are used to refer to the same object, and may be used interchangeably unless noted otherwise. - The
LED filament LED filament controller 50 shown inFIG. 1 . Thecontroller 50 may be configured to controlLEDs 210 of the LED filament individually. - In the context of this invention, the
LED filaments lighting device 100 shown inFIG. 1 can be described as follows.FIG. 2 for example, demonstrates cross sectional views of such anLED filament 20, with vertical line cuts along the width (FIG. 2 a ), and the length (FIG. 2 b ) of theLED filament 20. TheLEDs 210 are arranged on anelongated carrier 220, for instance a substrate. Please note that in this text the terms “carrier” and “substrate” may be used interchangeably, and unless stated otherwise, are meant to imply the same meaning. Preferably, theLED filament LED filament LED filament LED filament LED filament LED filament FIG. 2 b , or in a non-straight configuration such as for example a curved configuration, a 2D/3D spiral or a helix. - The
LEDs 210 may be arranged in at least one linear array. The linear array in which theLEDs 210 are arranged, may be in the direction of theelongated carrier 220. The linear array is preferably a matrix of N×M LEDs 210, wherein N=1 (or 2, or 3) and M is at least 10, more preferably at least 15, most preferably at least 20 such as for example at least 30 or 36LEDs 210. - The
carrier 220 may be rigid (made from e.g. a polymer, glass, quartz, metal or sapphire) or flexible (e.g. made of a polymer e.g. a film or foil). Acarrier 220 of rigid material may provide better cooling of theLED filament 20, meaning the heat generated by theLEDs 210 may be distributed by therigid substrate 220. Acarrier 220 of flexible material may provide shape freedom for designing the aesthetics of theLED filament substrate 220, may limit the shape design of theLED filament - As shown in
FIG. 2 b , thecarrier 220 may have a firstmajor surface 222, and a secondmajor surface 224. TheLEDs 210 are arranged on at least one of these surfaces. In the embodiment demonstrated inFIG. 2 b , and all of the following figures, theLEDs 210 are arranged on the firstmajor surface 222 of theelongated carrier 220. Thecarrier 220 may be reflective or light transmissive, such as translucent and preferably transparent. Thecarrier 220 may have a thickness of Tsubs. - According to this invention, the
LED filament 20 may comprise a first elongatedtransparent layer 230, situated such to (at least partially) cover theLEDs 210, and at least partially cover the firstmajor surface 222 of thecarrier 220. This is demonstrated in the cross-sectional views ofFIGS. 2 a and 2 b . A first elongatedlight scattering layer 240 is positioned so to cover the firsttransparent layer 230, such that the firsttransparent layer 230 is sandwiched between thecarrier 220 and thefirst scattering layer 240. The normal maximum distance D between alight output surface 215 of theLED 210 and thefirst scattering layer 240 represents the optical path forward-emitted light from theLED 210 will traverse in the firsttransparent layer 230. - The combined effect of the first
transparent layer 230 and thefirst scattering layer 240 is that they effectively provide for a mixing chamber, in which emitted light from theLEDs 210 in operation may be mixed. The scattering of light within thefirst scattering layer 240 may randomize the location from which light is emitted along the length L of theLED filament 20, hence providing a more homogeneous appearance of light exiting a first exitingsurface 245 of theLED filament 20. Some light may be backscattered from thefirst scattering layer 240 towards theelongated carrier 220. In the case of theelongated carrier 220 being transparent, the back scattered light may traverse the volume of thecarrier 220 and exit the filament from the secondmajor surface 224. -
FIG. 3 demonstrates cross sectional views of another embodiment of theLED filament 22 according to this invention, with vertical line cuts along the width, and the length (FIGS. 3 a and 3 b respectively). In the embodiment depicted in this figure, theLED filament 22 comprises a second elongatedtransparent layer 260 positioned to (at least partially) cover the secondmajor surface 224 of theelongated carrier 220, and a second elongatedlight scattering layer 250 positioned so to (at least partially) cover said second elongatedtransparent layer 260. The second elongatedtransparent layer 260 has a thickness of T2. The combined effect of the second transparent 260 and scattering 250 layers, is to effectively provide for a mixing chamber in which back scattered light from thefirst scattering layer 240, and side-emitted light from theLEDs 210 can be mixed, so to provide for a more homogeneous appearance for light exiting asecond exit surface 255 of theLED filament 22. In this embodiment thecarrier 220 should be light transparent, otherwise providing a mixing chamber on the secondmajor surface 224 of thecarrier 220 will be redundant. The secondtransparent layer 260 has a thickness of T2. Preferably D is larger than T2. This is to provide for a more optimal all-around light distribution from theLED filament 22. Also, the maximum normal distance P1 from the firstmajor surface 222 of theelongated carrier 220 to the exterior surface of the first elongatedlight scattering layer 240 may be at least 1.5 times the maximum normal distance P2 from the secondmajor surface 224 of theelongated carrier 220 to the exterior surface of the second elongatedlight scattering layer 250. - The
transparent layers layers carrier 220 on which theLEDs 210 are arranged on. Thetransparent layers - The scattering properties of the scattering layers 240, 250 may be achieved by through the inclusion of
light scattering particles - Furthermore, the scattering of the
first scattering layer 240 is preferably higher than that of thesecond scattering layer 250. That is for further improving the light mixing of forward-emitted light exiting the first exitingsurface 245 and the back scattered and/or side-emitted light from the second exitingsurface 255, so that they have a similar distribution, leading to an improved symmetry.FIG. 4 depicts exemplifying embodiments of anLED filament 22 in which thefirst scattering layer 240 is relatively more scattering than thesecond scattering layer 250. InFIG. 4 a the thickness S1 of thefirst scattering layer 240 is generally larger than the thickness S2 of thesecond scattering layer 250. By this the optical path through which forward-emitted light is required to traverse through thefirst scattering layer 240 is increased, so that consequently the average number of scattering events will be increased in comparison to light traversing thesecond scattering layer 250. InFIG. 4 b , the density and/or material of the scatteringparticles particles 242 of thefirst scattering layer 240 is higher compared to the scatteringparticles 252 of thesecond scattering layer 250. This may insure an increase in the average number of scattering events light may encounter in thefirst scattering layer 240 compared to that of thesecond scattering layer 250. It is additionally noted that in the embodiment ofFIGS. 4 b , S1 and S2 may be uniform. - A
first side surface 226 and asecond side surface 228 of theelongated carrier 220 of the embodiments depicted inFIGS. 1-4 are bare. It is noted that some of the light traversing through the thickness Tsubs of thecarrier 220 may escape through these first 226 and second 228 side surfaces. As mentioned, light may be mixed within the volume of the transparentelongated carrier 220, and additionally in the secondtransparent layer 260 in embodiments comprising a second transparent layer 260 (embodiments ofFIGS. 2-4 ), where the transparentelongated carrier 220 may be optically considered as a portion of the secondtransparent layer 260. Additionally, for ensuring a better all-around light distribution from thefilament 20 it may be useful that the first 226 and second 228 side surfaces of thecarrier 220 are also covered by a scattering layer. - In the embodiment of the
LED filament 24 depicted in the radial cross-sectional view ofFIG. 5 , the first 226 and second 228 side surfaces of thecarrier 220 are covered by ascattering layer 280. In this embodiment, thefirst scattering surface 240 and thesecond scattering surface 250 are merged so to form a single, all-aroundscattering layer 280, which circumferentially encompasses the rest of theLED filament 24. In the embodiment ofFIG. 5 , the scattering property of the all-aroundscattering layer 280 may differ from portion to portion in an angular gradient manner. This again, is to further improve the even all-around light distribution from thefilament 24. Theportion 228 of the all-aroundscattering layer 280 which is substantially parallel to theelongated carrier 220/light output surface 215 of theLED 210, has the highest scattering effect so to compensate for the higher intensity of the direct-emitted light from theLEDs 210, emitted in a direction substantially normal to that of theoutput surface 215 of theLEDs 210. Following the same reasoning, and as shown in the embodiment ofFIG. 5 , the angular scattering gradient of the single all-aroundscattering layer 280 is accomplished by a gradual change in the thickness of thisscattering layer 280. In addition, in the embodiment shown inFIG. 5 , the thickness, hence scattering properties of the all the single all-aroundscattering layer 280, has a mirrored symmetry around an axis X normal to the length of theelongated carrier 220. - The reflectivity, hence scattering, may be equal, and the lowest in portions R1-R4 of the single all-around
scattering layer 280. The latter mentioned portions, together with their mirrored portions, position-wise largely correspond to that of thesecond scattering layer 250 of the previous embodiments, and therefore is in no need of a gradient in scattering effects. These portions have a reflectivity of preferably less than 30%, more preferably less than 25%, most preferably less than 20%. - The reflectivity of portions R5-R8 have are higher than that of R1-R4, and have an increasing gradient in their reflectivity as follows: R5<R6<R7<R8. These portions together with their mirrored portions position-wise largely correspond with that of the
first scattering layer 240 of the previous embodiments, therefore are required to have a relatively higher scattering effect compared to R1-R4. Portion R8 has the highest reflectivity being preferably more than 50%, more preferably more than 60%, most preferably more than 70%. - The all-around
scattering layer 280 can be referred to as a diffuser. The scattering layer (diffuser) 280 can be made e.g. by dispensing, or a (shrink) tube. -
FIGS. 6 a through 6 c shows a schematic comparison of the light distribution resulting from different LED filaments. Thefilaments graph 600.FIG. 6 a depicts the light distribution E of aconventional LED filament 16 in which the carrier is reflective, thus light cannot traverse the carrier. As seen from theemission vectors 601, and the envelope light distribution E, light emitted from this LED is non-homogeneous, being less bright on the sides as opposed to the top, and is solely emitted from the first exiting surface. InFIG. 6 b light distribution E′ from afilament 17 which comprises a light transmissive carrier, and light scattering layers directly on both sides of the light transmissive carrier, is shown. As observable from theemission vectors 601, and the envelope light distribution E′, even though there is some emission from the backside of thefilament 17, the overall distribution is heterogeneous and non-symmetrical. This is due poor light mixing of thefilament 17.FIG. 6 c demonstrates light distribution E″ from afilament 24 according to the invention with the all-around light scattering layer (diffuser) 280. As observable from thegraph 600, the light distribution E″ of the filament with the diffuser is substantially homogeneous, with an all-around symmetrical light distribution. -
FIG. 7 demonstrates embodiments of theLED filament LEDs FIGS. 7 a and 7 b depict a portion of theelongated carrier 220, in whichR 212,G 214, andB 216 LEDs are arranged on the firstmajor surface 222 of thecarrier 220. InFIG. 7 a , TheR 212,G 214, andB 216 LEDs are arranged in three linear arrays: theR channel 12, theG channel 14, and theB channel 16 which are parallel and individually addressable, each contain theR 212,G 214, andB 216 LEDs respectively. (Each of theR 12,G 14, andB 16 channels may be addressed individually, and/or simultaneously.) -
FIG. 7 b illustrates a portion of thecarrier 220 in which theR 212, theG 214, and theB 216 LEDs are arranged alternately in a single linear array on the firstmajor surface 222, wherein theG LEDs 214 provide agreen channel 14, whereinR LEDs 212 provide ared channel 12, wherein theB LEDs 216 provide ablue channel 16. The in order to have separate color channels, theR 212,G 214, andB 216 LEDs may be connected using jumpers or adouble Cu layer 330 for connecting the same color LEDs to on another. Due to all LEDs being width-wise centrally arranged within the body of thefilament B channels -
FIG. 7 c depicts a portion of thecarrier 220 in which cool-white (color) 218, and warm-white (color) 219 LEDs arranged alternately in a single linear array. In this embodiment the warmwhite LEDs 219 provide a warmwhite channel 19, and the cool-white LEDs 218 provide a cool-white channel 18, such that thesechannels -
FIG. 7 d illustrates an embodiment in which the plurality of LEDs includered LEDs 212,green LEDs 214,blue LEDs 216, and white (e.g. cool or warm) LEDs 217 arranged alternately in a single linear array. - The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.
- Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.
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US20230358368A1 (en) | 2023-11-09 |
EP4115116B1 (en) | 2023-10-18 |
WO2021175711A1 (en) | 2021-09-10 |
JP7331267B2 (en) | 2023-08-22 |
EP4115116A1 (en) | 2023-01-11 |
EP4270498A2 (en) | 2023-11-01 |
JP2023507673A (en) | 2023-02-24 |
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US11739888B2 (en) | 2023-08-29 |
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